The present invention is directed toward radiation sensors and, more particularly, to novel methods for decreasing the hysteresis response of a radiation-responsive sensor by annealing of a member of radiation-conversion phosphor used therein.
Sensors used for detecting radiation flux, such as the x-ray flux detectors used in computed tomography systems, are known to the art. Such sensors may consist of a bar of a conversion material, such as thallium-doped cesium iodide (CsI:T1), which acts to convert x-ray flux to optical photons, and a photon detector positioned adjacent to the bar of conversion material, for converting the optical photons into an electric current, which may be amplified and subsequently processed to determine the x-ray flux incident upon the conversion material bar of the radiation sensor. The phosphor utilized in such a scintillation detection system has been found to be subject to a hysteresis effect, i.e. a reversible change in the optical photon output of the scintillation phosphor, with time and under constant radiation excitation. This phenomenom results in errors between consecutive measurements of incident radiation flux in scintillation detector systems. In radiation detection systems, such as computed tomography systems, where a high degree of accuracy is required, these errors have proven to be extremely undesirable. Accordingly, a method for reducing the hysteresis of the scintillation phosphor member, utilized in a radiation detector, is highly desirable.